Haskell has been designed for parallel and concurrent programming since
its inception. In particular, Haskell's purity greatly simplifies reasoning about
parallel programs. This page lists libraries and extensions for programming
concurrent and parallel applications in Haskell. See also the
parallel portal for research papers, tutorials and on
parallel and concurrent Haskell.

1.2 Monad-par

An alternative parallel programming API to that provided by the parallel package. The Par monad allows the simple description of parallel computations, and can be used to add parallelism to pure Haskell code. The basic API is straightforward: the monad supports forking and simple communication in terms of IVars.

1.4 Research tools

A complete, GHC-based implementation of the parallel Haskell extension GpH and of evaluation strategies is available. Extensions of the runtime-system and language to improve performance and support new platforms are under development.

2 Concurrency

GHC has supported concurrency with lightweight threads for more than a decade, and it is very fast. Threads in Haskell are preemptively scheduled and support everything you would normally expect from threads, including blocking I/O and foreign calls.

2.2 Actors

CHP is built on the ideas of CSP (Communicating Sequential Processes), featuring encapsulated parallel processes (no shared data!) communicating over synchronous channels. This is a very composable mode that also allows choice on communications, so that a process may offer to either read on one channel or write on another, but will only take the first that is available.

2.3 Helper tools

3 Distributed programming

3.1 MPI

hMPI is an acronym for HaskellMPI. It is a Haskell binding conforming to MPI (Message Passing Interface) standard 1.1/1.2. The programmer is in full control over the communication between the nodes of a cluster.

3.2 Distributed Haskell

GdH supports distributed stateful interactions on multiple locations. It is a conservative extension of both Concurrent Haskell and GpH, enabling the distribution of the stateful IO threads of the former on the multiple locations of the latter. The programming model includes forking stateful threads on remote locations, explicit communication over channels, and distributed exception handling.

Eden extends Haskell with a small set of syntactic constructs for explicit process specification and creation. While providing enough control to implement parallel algorithms efficiently, it frees the programmer from the tedious task of managing low-level details by introducing automatic communication (via head-strict lazy lists), synchronisation, and process handling.

3.3 Research tools

Haskell-Coloured Petri Nets (HCPN) are an instance of high-level Petri Nets, in which anonymous tokens are replaced by Haskell data objects (and transitions can operate on that data, in addition to moving it around). This gives us a hybrid graphical/textual modelling formalism for Haskell, especially suited for modelling concurrent and distributed systems.